The U.S. health care law’s process for providing insurance subsidies to middle-income families will produce a “burdensome, costly and frustrating quagmire,” a former Internal Revenue Service commissioner told a congressional committee.

The subsidies, structured as tax credits, are the main method in the 2010 law of helping Americans obtain health insurance. They will be delivered through exchanges — government-run markets that will connect people with insurance and cover part of the cost through federal payments to insurers. Such exchanges will be operated by states and the Department of Health and Human Services.

The exchanges, which will use income and household data to determine eligibility, will be performing a function that the IRS should be doing instead, former IRS Commissioner Fred Goldberg told a panel of the House Ways and Means Committee today.